Large Volume Injection of Polycyclic Aromatic Hydrocarbons

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1 JSB is an authorised partner of Large Volume Injection of Polycyclic Aromatic Hydrocarbons Application Note - Environmental #113 Author Anne Jurek Applications Chemist EST Analytical Cincinnati, OH Abstract Polycyclic Aromatic Hydrocarbons (PAHs) are formed from incomplete burning of carbon containing fuel. There are thousands of PAH compounds in the environment, and of those; there are several that have been established to be of concern for the environment. Extraction of PAH compounds involves a large amount of sample and solvent, and because of this, there is a lot of solvent waste. The use of Large Volume Injection (LVI) in conjunction with a Programmable Temperature Vaporizer (PTV) aids in eliminating some of this solvent waste, and reduces labor and shipping costs due to the ability to extract smaller volumes of sample without sacrificing sensitivity. This analysis will compare PAH compound response of a standard injection versus a large volume injection. Introduction: The most common practice for extraction of PAH compounds from a water matrix involves one liter of sample and more than 150mls of solvent. The sample goes through several liquid-liquid extraction and evaporation steps in order to achieve the final extract for sampling and analysis. USEPA Method 3511 proposes a micro-extraction technique that uses less than 5mls of sample and approximately 2mls of solvent. This technique is also much less time consuming. However, micro-extraction is not nearly as sensitive when analyzing for PAH compounds. In answer to this problem, laboratories can utilize Large Volume Injection in conjunction with a Programmable Temperature Vaporizer. When using this sampling technique, an analyst has the ability to inject several microliters of sample into the GC inlet, thus multiplying the amount of sample to be detected and analyzed by the MS. Consequently, sensitivity can be increased while extraction time and solvent use can be decreased. Discussion: As EPA detection limits get lower and lower, laboratories need to adapt to these expectations. Large Volume Injections enable laboratories to lower detection limits because the amount of sample introduced to the system is increased. Programmable Temperature Vaporization using solvent split mode is the usual technique for solvent elimination and pre-concentration of analytes. During vaporization, the analytes are transferred to the column for separation and analysis. When using LVI, the PTV inlet is set to solvent vent mode. The sample is introduced at a low temperature, and the solvent is eliminated using the purge flow to the split vent. The analytes are retained on the inlet liner while the solvent is vented. Next, the inlet is quickly heated in order transfer the analytes to the GC column in splitless mode. After the transfer, the inlet is set to purge any residual contaminants from the inlet.

2 ANNE JUREK Using LVI in conjunction with PTV enables laboratories to introduce more sample onto the GC column, therefore increasing sensitivity. This study will compare a 1µl injection of PAH compounds using a standard split/splitless injection to a 5µl injection of the same PAH compounds utilizing LVI and PTV. Experimental: The sampling system used for this analysis was the EST Analytical FLEX autosampler fitted with a 10µl liquid syringe. The Agilent 7890 GC and 5975 MS were used for separation and analysis. A Restek Rxi-5 Sil MS 30m x 250mm x 0.25µm column was mounted in the GC. The Agilent Split/Splitless inlet was used for the 1ul injections while the Titan PTV LVI was used for the 5ul injections. Refer to Tables 1 and 2 for the sampling and analysis parameters. Autosampler Flex (1µl) Flex (5µl) General Method Type Liquid Liquid Rinse Rinse Volume Rinse Fill Rate Rinse Cycles Rinse Dispense Rate 60% (6µl) 70% (7µl) 50% 50% % 100% Waste Depth 50% 50% Sample Sample Volume 10% (1µl) 50% (5µl) Rinse Volume 50% (5µl) 60% (6µl) Rinse Cycles 1 1 Pump Volume 50% (5µl) 60% (6µl) Pump Cycles 3 3 Air Volume Gap Air Fill Volume 10% (1µl) 10% (1µl) Single Injection Port Injection Rate Injection Volume Pre-Injection Delay 90% 90% 20% (2µl) 60% (6µl) 1 sec 1 sec Post Injection Delay 1 sec 1 sec Injection Start Output End End Rinse Rinse Volume Rinse Fill Rate Rinse Cycles 60% (6µl) 70% (7µl) 50% 50% 2 2 Rinse Dispense Rate 100% 100% Waste Depth 50% 50% Table 1: FLEX Autosampler Experimental Parameters

3 GC/MS Agilent 7890/5975 (1µl) Agilent 7890/5975 (5µl) Inlet Split/Splitless PTV Solvent Vent Inlet Temp. 280ºC 45ºC for 0.2 min, 200ºC/min to 125ºC for 0 min, 700ºC/min to 280ºC for 33.5min Inlet Head Pressure psi psi Split 20:1 NA Purge Flow to Split Vent NA 50ml/min at 1.5 min Vent Flow NA 100ml/min Vent pressure NA 0psi until 0.1min Cryo NA On at 50ºC Liner Column Oven Temp. Program Restek SKY liner, Splitless, Single Taper with Glass Wool, 4mm x 6.5 x 78.5 Rxi-5Sil MS 30m x 0.25mm I.D. x 0.25µm film thickness 45ºC hold for 4.0 min, ramp 10ºC/min to 320ºC hold for 2.0 min, 33.5 min run time TITAN XL SB Deactivated Liner with Glass Wool Rxi-5Sil MS 30m x 0.25mm I.D. x 0.25µm film thickness 45ºC hold for 4.0 min, ramp 10ºC/min to 320ºC hold for 2.0 min, 33.5 min run time Column Flow Rate 1.0ml/min. 1.0ml/min. Gas Helium Helium Total Flow 24ml/min 54.4ml/min. Source Temp. 230ºC 230ºC Quad Temp. 150ºC 150ºC MS Transfer Line Temp. 280ºC 280ºC Solvent Delay 5.0 min 5.0 min Acquisition Mode Scan Scan Scan Range m/z m/z Sampling Rate 3.12 scans/sec 3.12 scans/sec Table 2: GC/MS Experimental Parameters The PAH standards were acquired from Restek. Two different curves were run for the experiment. The 1µl injection curve standard range was from 0.5 ppm to 200ppm or 0.50 to 200ng on column. For the large volume, 5µl, injection the standard range was from 0.05ppm to 50ppm or 0.25 to 250ng on column. Next seven replicates of the low standard were run in order to determine MDLs. Finally, in order to ascertain the precision and accuracy of the injection techniques, seven replicates of the mid-point of each curve were run. Experimental results are listed in Table 3 and 4, while the chromatograms of the two injections are displayed in Figures 1 and 2.

4 1µl Injection, Standard Injection Compound Curve Ave. %RSD %Recovery MDL %RSD Curve RF 50ng 50ng Naphthalene Acenaphthalene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-cd)pyrene Dibenz(a,h)anthracene Benzo(g,h,i)perylene Ave Table 3: Experimental Results Summary 1µl Injection 5µl Injection, Large Volume Injection Compound Curve Ave. %RSD %Recovery MDL %RSD Curve RF 50ng 50ng Naphthalene Acenaphthalene Acenaphthene Fluorene Phenanthrene Anthracene Fluoranthene Pyrene Benz(a)anthracene Chrysene Benzo(b)fluoranthene Benzo(k)fluoranthene Benzo(a)pyrene Indeno(1,2,3-cd)pyrene Dibenz(a,h)anthracene Benzo(g,h,i)perylene Ave Table 4: Experimental Results Summary 5µl Injection

5 Figure 1: 50ng on column, 1ul Injection Conclusions: Figure 1: 50ng on column, 5ul Injection The LVI technique, in conjunction with PTV, enabled the curve range to go down to 0.25ng on column without sacrificing compound response. The ability to inject more than one microliter of sample onto the GC column enhances the sensitivity of the system. When comparing the results of a standard injection to an LVI, the linearity, compound response, detection limits, and precision and accuracy were all comparable. Consequently, the use of LVI in conjunction with the FLEX Autosampling system is a viable option for PAH analysis. Furthermore, as detection limits become more and more stringent, the volume of the injection can increase in order to accommodate the new requirements. EST analytical and JSB shall not be liable for errors contained herein or for incidental or consequential damages in connection with this publication. Inform ation, descriptions, and specifications in this publication are subject to change without notice Headquarters JSB International Tramstraat CM Eindhoven T +31 (0) F +31 (0) With courtesy of Zoex Europe Tramstraat CM Eindhoven T +31 (0) F +31 (0) Sales and Service Netherlands Apolloweg 2B 8239 DA Lelystad T +31 (0) F +31 (0) Belgium Grensstraat 7 Box Diegem T +32 (0) F +32 (0) Germany Max-Planck-Strasse 4 D Kamp-Lintfort T +49 (0) F +49 (0) UK & Ireland Cedar Court, Grove Park Business Est. White Waltham, Maidenhead Berks, SL6 3LW T +44 (0) F +44 (0) info@go-jsb.com